Assuming none of these face eachother first
Link/Ganon
Cloud/Seph
Mario/Bowser
Sonic/Knux
Snake/Whoever his rival is
X/Zero
Charizard/Blastoise (or Red/Blue/some other Pokemon pairing)
Left Pong Paddle/Right Pong Paddle (will probably win it all tbqh)
--
SephirothG, channeling awesomeness from Mershiness.
The Resurrection